outdoor low-voltage lighting

Low-voltage outdoor lighting uses 12 volt instead of the common household 110/120 volts. Low-voltage is energy-efficient, and also cheap and easy to install – a reason that explains its increasing popularity.

Be careful, however: use low-voltage outdoor lighting only and where necessary. And do not forget controls (timers, photocells...) that can be used to avoid light pollution.

Low-voltage outdoor kits

There are many pre-packaged kits with all the correspondent components:

- the transformer (or power back),
- cables and
- fixtures.

Kits are often conceived to be expanded: you can add lights in the future as necessary, or you can purchase a second (and a third…) kit to expand your system.

Prices

Prices of some inexpensive kits range from $15 to $100, but the best ones are $300 and more. All depends on the number and type of fixtures and materials. Be aware: low prices usually mean low quality and non-friendly environmental solutions.

Lamps

The low voltage lamps are, obviously, the kit’s source of light. Lamps can be of very different types and watts. Halogen lamps are the most common, but the market is beginning to offer low-voltage fluorescent, which you should prefer whenever the lights are going to be on for more than 2-4 hours.

Obviously, you should use lights rated for outdoor use: see Compact Fluorescent Lamps.

Fixtures

There are many options concerning low-voltage fixtures, but many of them are of poor quality and a source of light pollution.

Prefer Energy Star and European Union Eco-labelled qualified fixtures; or fixtures supported by organizations like the The International Dark Sky Association or the Underwriters Laboratories. These products may involve higher initial costs, but they have quality and durability, besides being environmentally-friendly.

Outdoor lighting fixtures should be water-resistant and rated for outdoor use.

Transformers (Power-Backs) and outlets

Outdoor Low-Voltage Low-voltage transformers are conceived to plug into standard outlets in order to reduce the 110/120 volts household current to 12 volts.

Many transformers, even the cheaper, have automatic timers in order to switch lights on/off at preset times. Configurations are variable, but even cheaper and common 100-watt transformers have a manual on/off switch and an automatic timer.

The outlets used by transformers are usually outdoor ones, but transformers may also use indoor outlets (in that case, the transformer should be rated for inside use).

Options

The number of garden lights/fixtures that can be connected to a particular transformer depends on its capacity and on the wattage demanded by the fixtures. If the transformer is, say, 100-watt, then the total wattage of the lights should not exceed 100 watts (10 garden lights with 10-watt bulbs, for instance).

In the above example, to install 20 or more lights (instead of 10) you would have to purchase a second/third transformer… The alternative to these standard packages, is to buy a bigger transformer and configure a less standardized system: the size of transformer, in this case, depends on the number of light fixtures you may want to install...

Some basic calculations will be needed, in this case. If, for instance, you intend to install 10 path lights of 18 watts (180 W) and 2 down-lighting lights of 50 W (100 W) then you will need a 300-watt transformer – or a larger one to allow future expansions (the-extra wattage should not exceed one-third of the total needs). Typically, transformers can range from 150 W to 900 W.

Low voltage cable

Low-voltage cable must be weather-resistant. Typically they begin and end at the transformer (creating a looped run).

Popular sizes include 12-, 14- and 16-gauge (gauge depends on the amount of watts required to operate the system). Typically, 16-gauge cable can carry 150 watts, while 14-gauge cable can carry 200 watts and 12-gauge (the standard wire gauge) cable can carry 300 watts.

Installation & Low-voltage outdoor lighting

Some pre-packaged low-voltage systems are relatively simple and safe to install and may not demand a professional electrician.

Take into account some basic design techniques. See: Landscape lighting design.